Working green roof unveiled at Ambler
It’s difficult to imagine a less natural setting than an urban center such as Philadelphia, where it can be rare to see any vestige of the natural environment amid the gray-shaded mosaic of steel, stone and glass.
And yet just a few miles outside the city, students and teachers at Temple University Ambler’s landscape architecture and horticulture department are doing their part to speed up the urban greening process.
Through research and demonstration of green roof technology at the Ambler Campus, they are developing the ability to restore cities like Philadelphia to William Penn’s vision of a “green country town” — this time, from the top down.
A leader in the field
The use of green roof technology, already popular in Europe and parts of Asia, is slowly expanding in the United States.
Green roofs are a living biological community of plants and microorganisms growing in a lightweight medium that provide an environmentally sound alternative to a traditional roof system. The technology is believed to help reduce the “heat effect” that occurs in cities, and is becoming more common in the United States and around the world.
At the 2002 Philadelphia Flower Show, Temple landscape architecture and horticulture students provided the inspiration for the current green roof research taking place at the Ambler Campus, bringing home a Best in Show Award in the Academic Educational category for a comprehensive green roof technology exhibit. Three years later, Temple remains at the forefront of green roof technology research.
On Oct. 11, Temple Ambler unveiled a demonstration rooftop garden on the campus’ new Intercollegiate Athletics Field House, built with the assistance of a $50,000 grant from PECO.
The new green roof will tie directly into the mission of the Landscape Arboretum of Temple University Ambler in promoting an understanding of the relationship between people and the environment and “awareness of both the need for and the means to achieve greater environmental responsibility,” according to arboretum director Jenny Carey.
“We believe that roof gardens can have a beneficial effect on the environment, but we’re not going to reap that benefit until there are more people who understand and are willing to embrace the technology,” she said. “A physical demonstration that people can see and experience will help answer many of the questions they might have and, hopefully, alleviative some of the resistance there might be for this concept.”
A living laboratory
The green roof garden will provide substantial educational and research opportunities for students and faculty. Horticulture senior lecturer Sinclair Adam, landscape architecture assistant professor Skip Graffam and horticulture assistant professor Jun Yang are researching the types of plants that would be most viable for green roof plantings in the region.
The plants that make up Ambler’s PECO Green Roof Garden are made up of several species, most notably many types of sedums — a drought- and humidity-tolerant succulent plant, typically with thick, waxy leaves — and della spermum, another succulent that often goes by the name “freeway daisies” or “ice plants” for their hardiness and need for little maintenance.
“We are doing research in our greenhouse to determine plants that can endure the elements, such as greater extremes of heat and cold. Currently, we’re checking sedums and experimenting with growth rates,” Adam said. “It’s an opportunity for our students to observe how this technology is moving forward and will essentially act as a ‘lab’ building for us to conduct actual measurements.”
According to Adam, the next step in developing the already growing green roof “is to acquire a number of native plants to continue to develop the roof system for our research.”
Proposed research involving the new green roof garden includes the acquisition, study and cultivation of new plant material; continued study of the green roof’s impact on energy efficiency, water quality, water retention and roof temperature; development of a green roof course and additional independent study programs; and increased educational outreach programs to promote green roof technology.
Evaluation of the green roof runoff will include measurements of nitrates, phosphates, pollutants and other water quality measurements. The potential impact of green roof technology on storm water management will be evaluated by measuring the volume of water held by the green roof system during storms.
All of the research is also providing students in the landscape architecture and horticulture programs with real-world, hands-on experience, a cornerstone of both programs. The green roof garden is a living laboratory — one of the many teaching gardens of the Landscape Arboretum of Temple University Ambler — for students and the public to learn and take inspiration from.
- By Jim Duffy
A green roof primer
|• Green roofs are alive; a living biological community of plants and microorganisms growing in a lightweight medium that provide an opportunity to revitalize urban landscapes ecologically, economically and socially.
• Modern green roof technology was pioneered in Germany more than 30 years ago and has become a staple of design in many European countries — 12 percent of all flat roofs in Germany are green roofs. In the past few years, interest into green roof technology has begun to take root in the United States.
• Nearly 50 percent of the world’s population and more than 220 million Americans live in densely developed urban environments.
• This transformation of the Earth’s surface and termination of its biological processes has resulted in a deteriorating air quality, degraded water, and devastating urban “heat islands” — traditional roofs generate intense reflective heat. In warm climates, when air temperatures can reach 95°F or higher during the summer, roof surface temperatures can reach 175°F. An increase in the outside air temperature over roof surfaces contributes to and accelerates the chemical reaction that creates low atmospheric ozone, a primary component of smog.
• By their nature, green roofs mimic the natural processes that buildings replace. The plant system has a positive impact on air, noise and water pollution — atmospheric pollutants carried in rainwater are filtered through the plants and microorganisms, effectively serving as a bio-filter for improving water quality.
• Green roofs provide extra insulation, helping to conserve energy in the winter and in the summer when the green roof substantially decreases roof temperatures, making it easier to cool the structure — temperature differentials between green roofs and non-greened roofs can be more than 20 degrees on the roof surface.
• Green roofs contribute to better stormwater management by trapping more water on the roof during a storm and decreasing the speed with which stormwater makes its way into the ground systems — an important aspect of the technology, considering the attention focused on flood mitigation in the wake of an intense hurricane season.
• Green roofs potentially increase the local biodiversity by providing habitat areas previously unavailable for animal life, particularly for nesting birds.
• There are a few significant examples of green roof technology in use in the United States, including Atlanta City Hall; the Seattle Justice Center; Ford Motor Co.’s Rouge River plant in Dearborn, Mich.; Chicago City Hall; Rockefeller Center in New York; the Fencing Academy of Philadelphia, and now the PECO Green Roof Garden at Temple University Ambler.
• A typical green roof may consist of several layers, from top to bottom: sedum plants, which trap dust, absorb carbon dioxide, release oxygen and create habitat; vegetation blanket, a semi-organic material containing shale, sand, peat, compost and dolomite; fleece, a felt-like absorbent mat of mineral wool that holds water; a drainage layer; and a root-resistant membrane, which protects the underlying roof from water and root damage.
• There are two types of green roof systems currently being created in European and American cities. Intensive green roof systems utilize planting media depths greater than one foot that can support small trees and shrubs. Extensive green roof systems generally have planting media depths of less than one foot that support low-growing plants with a shallow root base. The PECO Green Roof is of the extensive variety, supporting colonies of carefully selected plants, all native to the region, in approximately 6 inches of a lightweight medium (shale mix). Extensive green roofs have much broader potential for replication on buildings in the United States.